Digital imaging sensors are employed in many devices and systems to capture images, such as in digital cameras. Imaging sensors employ large semiconductor arrays of detection pixels that can comprise charge-coupled devices (CCDs) or complementary metal oxide semiconductor (CMOS) devices, among others. The imaging sensors can be configured to capture a range of the electromagnetic spectrum that spans both visible light and infrared light ranges.
Specialized imaging sensors can be employed in time-of-flight (ToF or TOF) camera systems. ToF sensing devices share some aspects of visible wavelength sensors, such as RGB imaging sensors, but also have some unique characteristics. ToF cameras measure a three dimensional representation of a scene using emission of light that is precisely timed to measurement or detection by an imaging sensor. Some ToF systems use a differential pixel structure within an integrated array of pixels that can detect incident light during associated detection phases. These ToF cameras can be employed in applications where identifying relative depths among objects in a scene is useful, such as interactive gaming devices, virtual reality devices, augmented reality devices, industrial controls, medical scanners, or other devices.
Overview
Pixel arrangements in time-of-flight sensors are presented that include sensing elements that establish charges related to incident light, charge storage elements that accumulate integrated charges transferred from the sensing elements, and diffusion nodes configured to establish measurement voltages representative of the integrated charges that are dumped from the charge storage elements. The pixel arrangement includes analog domain output circuitry comprising a measurement capacitance element that stores the measurement voltage, and a reset capacitance element that stores a reset voltage established at the diffusion node during a reset phase performed prior to a measurement phase. The analog domain output circuitry subtracts the stored reset voltage from the stored measurement voltage for processing into a pixel output voltage that at least partially reduces readout voltage uncertainty (such as kTC noise) of the pixel arrangement.
This Overview is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. It may be understood that this Overview is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.